The invention relates to a hot gas or Stirling engine whose cylinder chambers are connected via heating tubes, which extend through a heating chamber, with regenerator-cooler units.
In the case of hot gas or Stirling engines whose cylinder chambers are connected via heating tubes, which extend through a heating chamber, with regenerator-cooler units, the regenerators have been generally limited to the axial flow type. In this respect, dependent on the design of the engine, a distinction has been made between cylindrical regenerators, which are respectively housed together with a separate cooler, that is disposed axially to the rear thereof, in their own housings arranged adjacent to the associated cylinders, on the one hand, and, on the other hand, annular cylindrical regenerators, which are respectively accommodated together with coolers, which are also annular cylindrical and are arranged thereunder, coaxially to the respectively associated cylinders in the engine housing. These two principles of design are illustrated together in FIG. 3.5.2-6 on page 112 of the publication DOE/NASA/0032-79/5, NASA CR-159744, MTI 79 ASE 101QT6, entitled "Automotive Stirling Engine Development Program" quarterly technical progress report for period July 1-Sept. 30, 1979, Mechanical Technology Incorporated, January 1980. The key feature of the two designs is that the respective regenerator is precisely fitted as a prefabricated unit in a receiving space the configuration and diameter of which are adapted to the dimensions of the regenerator. Furthermore, whatever its particular design, the regenerator is such that the working gas is only able to enter and leave via its ends and is only able to flow axially through it. The ultimate flow area available for the working gas was for this reason limited by the diameter of the receiving space for the regenerator.
Thus, especially in the case of hot gas or Stirling engines with a large displacement and with regenerators which, hence, have to be large as well, the relatively high working gas pressure of approximately 160 bar leads to mechanical strength problems in the regenerator housing and the engine housing, respectively. These problems have so far only been dealt with by having regenerator housings or engine housing which are either manufactured of materials with a greater resistance to pressure or with suitably thicker walls. Both features, however, ultimately led to a substantial increase in the price of the engine. In the case of annular cylindrical regenerators arranged coaxially to the cylinders any increase in the thickness of the walls in the engine housing led furthermore to an increase in the distance between the cylinders and consequently to an increase in the length of the engine, which was not desired.
Accordingly, it is an object of the present invention to provide a systematic modification of the regenerators so that the above mentioned disadvantageous features may be avoided in the case of engines with a large displacement and with high working gas pressures.